public class ValueOfFraction {
    public static void main(String[] args) {
        double n = 1;
        double h = 0;
        for(n = 1;n < 100.0;n++) {
            if(n%2 == 0) {
                h -= 1/n;
            } else {
                h += 1/n;
            }
        }
        System.out.println(h);
    }
}
